You must use the range supplied by the laboratory that performed your test to evaluate whether your results are “within normal limits.” While the accuracy of laboratory testing has significantly evolved over the past few decades, some lab-to-lab variability can occur due to differences in testing equipment, chemical reagents used, and analysis techniques. Consequently, for most lab tests, there is no universally applicable reference value. This is the reason why so few reference ranges are provided in the test information on this website, Lab Tests Online.

While having all test results within normal limits is certainly a good sign, it’s not a guarantee. For many tests, there is a lot of overlap among results from healthy people and those with diseases, so there is still a chance that there could be an undetected problem. Lab test results in some people with disease fall within the reference range, especially in the early stages of a disease.

Almost every child or adult that has a lab test done has at least one value that is not within normal limits. A test result outside the reference range may or may not indicate a problem. Since many reference values are based on statistical ranges in healthy people, you may be one of the healthy people outside the statistical range, especially if your value is close to the expected reference range. For example, a liver enzyme such as AST or ALT being three (3) points over the normal range is typically no reason to worry. However, white blood cell counts that drop below normal limits by a few tenths of a point may be an indication that your child is more susceptible to infection and needs to take appropriate cautions. Your healthcare team can help you make sense of which levels that are ‘outside of normal limits’ are truly ones to watch.